The present invention relates to a polyester type conjugate fiber package obtained by a single-stage melt-spinning method, a method for producing the same and a false-twist texturing method thereof.
Polyethylene terephthalate (hereinafter referred to as PET) fiber has been mass-produced throughout the world, to establish a large industry, because it is most suitable for the clothing use.
Polytrimethylene terephthalate (hereinafter referred to as PTT) fiber is known from prior art documents such as J. Polymer Science: Polymer Physics Edition: Vol. 14, p 263 to 274 (1976), Japanese Unexamined Patent Publication (Kokai) No. 52-5320 or WO-99/27168.
There is a disclosure in these prior art documents in that a fabric using PTT fibers having a proper elongation at break, thermal stress and/or shrinkage in boiling water has a low modulus to exhibit a soft hand touch and is suitable for the clothing such as inner wear, outer wear, sportswear, hosiery, lining cloth or swim suits.
On the other hand, polyester conjugate fibers of a side-by-side type or an eccentric sheath/core type have been known as fibers capable of providing a fabric with a bulkiness without being subjected to a false-twist texturing process.
As a PTT type conjugate fiber characterized by a soft hand touch, there is a conjugate fiber in which PTT is used as at least one of its components or a conjugate fiber in which PTTs having different inherent viscosities are used as both components (hereinafter, these are referred to as polyester type conjugate fibers), as disclosed in Japanese Examined Patent Publication (Kokoku) No. 43-19108, Japanese Unexamined Patent Publication (Kokai) Nos. 11-189923, 2000-239927, 2001-55634, EP 1059372, Japanese Unexamined Patent Publication No. 2001-131837, U.S. Pat. No. 6,306,499, WO 01/53573 or US 2002-0025433. These prior art documents describe that the polyester type conjugate fiber is characterized by a soft hand touch and a favorable crimp developing property which characteristics are suitable for various stretch fabrics or bulky fabrics.
In general, when the polyester type conjugate fiber is produced by a melt spinning method, there are a two-stage method in which an undrawn fiber once wound as a package is drawn to be a drawn fiber and a single-stage method in which the spinning and the drawing are continuously carried out in one process.
In Japanese Unexamined Patent Publication (Kokai) Nos. 2001-131837, 2001-348734 and 2002-61031, a so-called direct spin-draw method is proposed when the polyester type conjugate fiber is produced, in which the spinning and the drawing are continuously carried out in one stage.
Particularly, in Japanese Unexamined Patent Publication No. 2001-131837, a polyester type drawn conjugate fiber is disclosed, which has a stretching elongation of 10% or more even under a load of 3.5xc3x9710xe2x88x923 cN/dtex by controlling a thermal shrinkage stress thereof to be 0.25 cN/dtex or more. This polyester type drawn conjugate fiber can be hard-twisted and used for a woven fabric having a large structural-constraint force, in which fabric the fiber develops a high crimpability.
Methods for obtaining a pre-oriented fiber to be false-twisted are disclosed in Chemical Fibers International: Vol. 47. p72 to 74 (February, 1997), and Japanese Unexamined Patent Publication (Kokai) Nos. 2001-20136 and 2000-256918. In these documents, as a pre-oriented fiber to be false-twisted, a fiber consisting solely of PTT or a polyester type conjugate fiber is disclosed, which is wound at a speed of 2000 to 6000 m/min without using a godet roll or with a cold godet roll.
According to the study of the present inventors, the polyester type pre-oriented conjugate fiber or drawn conjugate fiber obtained at a high spinning speed has a high orientation degree but a low crystallinity. Such a pre-oriented conjugate fiber or drawn conjugate fiber has a glass transition temperature in a range from approximately 35 to 45xc2x0 C. and is extremely sensitive to temperature and humidity.
In a spinning process, there is a phenomenon in that the heat generation of a motor of a winder running at a high speed is transmitted to a package via a bobbin shaft to increase the package temperature. Also, the package temperature rises by the heat generated due to the friction between the package and a presser roll. It has been also apparent that, if the package temperature is increased by such causes, the pre-oriented conjugate fiber or drawn conjugate fiber shrinks in the package during the winding.
The shrinkage of the pre-oriented conjugate fiber or drawn conjugate fiber hardly occurs in package-selvage portions (hereinafter referred merely to as selvage portions) in which the fiber is layered to have a high winding hardness, but solely occurs in the fiber layered in the remaining portion (hereinafter referred to as a central portion). As a result, the package is of a high-selvage shape during the winding. Once the high-selvage shape is formed, the selvage portion is alone in contact with the presser roll and the frictional heat is further concentrated to the selvage portion as a winding weight of the package increases.
The resultant package thus wound to have a predetermined diameter is of a so-called high-selvage shape wherein a (winding) diameter of the selvage portion is larger than that of the central portion. FIG. 1 is a schematic illustration of a package in a non-high-selvage shape, and FIG. 2 is a schematic illustration of a package in a high-selvage shape.
The high-selvage shaped package not only has a difference in diameter but also has a large difference in fiber property as described later, such as a thermal characteristic, yarn fineness and the number of crimps, between the selvage portion and the central portion.
In addition, as a winding weight increases, a lateral end surface of the package tends to be bulged outward due to the fiber shrinkage to form a so-called bulge whereby it is impossible to remove the package from the winder.
(i) Difference in Dry Heat Shrinkage Stress Value
The polyester type conjugate fibers in the selvage portion and the central portion of the package are different from each other in dry shrinkage stress value obtained by the measurement of the heat shrinkage stress described later. That is, the dry heat shrinkage stress value of the conjugate fiber in the selvage portion is higher than that of the conjugate fiber in the central portion.
It has been apparent that the difference in heat shrinkage characteristic becomes apparent as a difference in shrinkage or crimpability of a fabric during the dyeing process to cause a drawback of appearance quality such as a tight yarn or a puckering.
(ii) Variation in Yarn Fineness
The variation in yarn fineness of the pre-oriented conjugate fiber or drawn conjugate fiber is a periodic variation corresponding to a fiber length from one of the selvage portions of the package to the other (1 stroke or 2 strokes).
Charts measuring the variation in yarn fineness of the pre-oriented conjugate fiber or drawn conjugate fiber unwound from the package by an evenness tester are shown in FIGS. 3 and 4. FIG. 3 is a chart corresponding to the package of FIG. 1 and FIG. 4 is a chart corresponding to the package of FIG. 2. In the measurement charts, the periodic variation is observed by downward pin-like signals appearing at an equal pitch on a lower yarn fineness side. The existence of the downward signal means that a yarn fineness of the fiber (yarn thickness) at this point in the fiber length direction fluctuates to the smaller side.
It has been apparent that such a variation in yarn fineness causes a periodic dyeing unevenness in a false-twist textured yarn or a fabric.
(iii) Apparent Crimp
The polyester type conjugate fiber is characterized to have a latent crimpability capable of developing the crimp after the heat treatment. However, there may be a case in which the crimp has already been developed while the fiber is maintained as being wound in the package. This is the apparent crimp.
As the apparent crimp can cause a rise in the unwinding tension when the polyester conjugate fiber is unwound from the package at a high speed, it is preferably lowered.
As described before, it has been apparent that the polyester type conjugate fiber wound in the selvage portion of the package is liable to develop the apparent crimp in comparison with the fiber wound in the central portion.
For instance, there may be a case in which the apparent crimp exists in the selvage portion even if no apparent crimp exists in the central portion. When the polyester type conjugate fiber is unwound from such a package at a high speed, it has been apparent that the unwinding tension fluctuates due to apparent crimp to generate the yarn breakage during the false-twist texturing process or the weaving/knitting process.
(iv) High-speed Unwinding Property
A plain weave fabric represented by taffeta or twill or a warp knit fabric such as a tricot fabric is adopted for the clothing such as a lining cloth or a innerwear. Since a raw fiber not processed by a false-twist texturing or the like is often used for these fabrics, the arrangement of the fibers in the fabric is regular. Thus, there is a problem in that the drawback existing in the fiber is directly apparent as a fault in the fabric such as a streaky warp, a tight weft or a dyeing unevenness.
Recently, a cost competition has become severe in the weaving or knitting process and the processing speed has been higher in correspondence thereto. For example, a warping speed in the preparation of warp yarns for the woven fabric increases from the conventional range of from 100 to 200 m/min to a recent range of from 500 to 1000 m/min. Also, a weft-picking speed in the loom is as fast as in a range from 800 to 1500 m/min in an industrial process.
If the fluctuation of the unwinding tension corresponding to the yarn length from one end surface to the other end surface of the package is large during the unwinding of the polyester type conjugate fiber from the package at a high speed, the yarn breakage increases. Also, if the difference between the maximum value and the minimum value of the tension fluctuation (hereinafter referred to as the difference in unwinding tension) is large, a periodic quality fault occurs in the fabric, such as a tight yarn or others.
FIG. 7 is a chart showing a fluctuation of the the unwinding tension when the polyester type conjugate fiber is unwound at a high speed from the package having a favorable winding shape shown in FIG. 1. FIG. 8 is a chart showing a fluctuation of the unwinding tension when the polyester type conjugate fiber is unwound at a high speed from the package having an unfavorable winding shape shown in FIG. 2.
In FIGS. 7 and 8, a horizontal axis represents a yarn length of the polyester type conjugate fiber and a vertical axis represents an unwinding tension.
Accordingly, in any case when the polyester type conjugate fiber package having the above-mentioned drawbacks therein is used for the knitting or the weaving as it is without being drawn or when it is used for the knitting or the weaving after being drawn and false-twisted, the resultant dyed fabric generally is unfavorable in dyeing uniformity and exhibits a periodic unevenness of dyeing or luster. Thus, it has been apparent that the economical value of the fabric which is a final product is significantly deteriorated. Such a drawback cannot be solved even though the high-selvage shape of the package is eliminated to some extent.
Either of the packages disclosed in Japanese Unexamined Patent Publication (Kokai) Nos. 2001-131837 and 2001-348734 have the above-mentioned periodic drawbacks therein because the heat shrinkage of the conjugate fiber is large and the high-selvage shape is significant during the winding process.
Accordingly, there has been no polyester type conjugate fiber, obtained by the single-stage melt-spinning method in the prior art, which is capable of producing a fabric free from periodic dyeing unevenness, good in dyeing uniformity and excellent in dignity as well as no polyester type conjugate fiber package excellent in high-speed unwinding capability.
An object of the present invention is to provide a polyester type conjugate fiber package obtained by a single-stage melt-spinning method and suitable for the clothing use. The polyester type conjugate fiber obtained by the present invention is smoothly unwound from the package at a high speed and provided to the knitting/weaving process as it is without being drawn, or it is provided to the knitting/weaving process after being false-twisted or draw-textured. The resultant fabric is free from periodic dyeing unevenness and excellent in dyeing uniformity as well as stretchability and stretch-back property.
Another object of the present invention is to provide a method for false-twisting a polyester type pre-oriented conjugate fiber.
The problems to be solved by the present invention are to eliminate the prior art drawbacks in the polyester type conjugate fiber package obtained by the single-stage melt-spinning method, such as the tension fluctuation during the high speed unwinding, the heat shrinkage characteristic, the yarn fineness variation characteristic and the crimp characteristic resulting from the high-selvage shape of the package as well as the periodic dyeing unevenness in the yarn length direction.
The present inventors have diligently studied to solve the above problems and found that they can be solved by specifying the spinning conditions and the winding conditions of the polyester type conjugate fiber when it is spun and wound with or without being drawn.
That is, the present inventors have found that it is possible to eliminate various drawbacks generated in the selvage portion of the polyester type conjugate fiber package during the winding thereof by specifying an extruding conditions and a spinning tension during the spinning process, a temperature and a winding speed of the package during the winding thereof in the production of the conjugate fiber. The polyester type conjugate fiber package obtained by the above method has the specific range of the heat shrinkage characteristic and the yarn fineness variation characteristic both in the selvage portion and the central portion, whereby it is excellent in high-speed unwinding property. The resultant polyester type conjugate fiber can be provided to the knitting/weaving process as it is without being drawn or after being draw-textured. The obtained fabric is free from the periodic dyeing unevenness and excellent in dyeing uniformity as well as in stretchability and stretch-back property.
The present invention is as follows:
1. A package of polyester type conjugate fiber of either a side-by-side type or an eccentric sheath/core type in which two kinds of polyester components are adhered to each other to form a single filament, wherein at least one of the components consisting of the single filament is polytrimethylene terephthalate containing repeating units of trimethylene terephthalate of 90 mol % or more, which package is formed of 2 kg or more of the conjugate fiber and satisfies the following items (1) to (3):
(1) the difference in diameter between a selvage portion and a central portion of the package is 10 mm or less,
(2) a winding width of the package is in a range from 60 to 250 mm and a diameter of the package is in a range from 100 to 400 mm, and
(3) the difference in dry-heat shrinkage stress value between the conjugate fibers layered in the selvage portion and the central portion of the package is 0.05 cN/dtex or less.
2. A package of polyester type conjugate fiber as defined by the above 1, wherein the difference in dry-heat shrinkage stress value between the conjugate fibers layered in the selvage portion and the central portion of the package is 0.01 cN/dtex or less.
3. A package of polyester type conjugate fiber as defined by the above 1 or 2, wherein the conjugate fiber layered in the package is a pre-oriented conjugate fiber having an elongation at break in a range from 60 to 120%.
4. A package of polyester type conjugate fiber as defined by the above 1 or 2, wherein the conjugate fiber layered in the package is a drawn conjugate fiber having an elongation at break in a range from 25 to 80%.
5. A package of polyester type conjugate fiber as defined by any one of the above 1 to 4, wherein a yarn fineness variation value U % of the conjugate fiber unwound from the package is 1.5% or less and a variation coefficient of a yarn fineness variation period is 0.4 or less.
6. A package of polyester type conjugate fiber as defined by any one of the above 1 to 5, wherein the relationship between the difference xcex94F (cN/dtex) in unwinding tension during the unwinding of the conjugate fiber from the package and an unwinding speed u (m/min) satisfies the following formula (1):
xcex94Fxe2x89xa68.0xc3x9710xe2x88x926uxe2x80x83xe2x80x83(1)
7. A package of polyester type conjugate fiber as defined by any one of the above 1 to 6, wherein a bulge percentage of the package is 12% or less.
8. A package of polyester type conjugate fiber as defined by any one of claims 1 to 7, wherein a stretching elongation Vc of the conjugate fiber layered in the selvage portion of the package is 20% or less prior to being treated with boiling water.
9. A package of polyester type conjugate fiber as defined by any one of the above 1 to 8, wherein a hardness of the selvage portion of the package is in a range from 50 to 90 and the difference in hardness between the opposite selvage portions is 10 or less.
10. A package of polyester type conjugate fiber as defined by any one of the above 1 to 9, wherein a density of the package is in a range from 0.80 to 0.92 g/cm3.
11. A package of polyester type conjugate fiber as defined by any one of the above 1 to 10, wherein either of the two kinds of polyester components is polytrimethylene terephthalate containing 90 mol % or more of the repeating units of trimethylene terephthalate.
12. Polyester type pre-oriented conjugate fiber of either a side-by-side type or an eccentric sheath/core type in which two kinds of polyester components are adhered to each other to form a single filament, wherein at least one of the components consisting of the single filament is polytrimethylene terephthalate containing repeating units of trimethylene terephthalate of 90 mol % or more, and wherein the pre-oriented conjugate fiber is wound to form a package and satisfies the following items (1) to (4):
(1) a stretching elongation Vc prior to being treated with boiling water is less than 20%,
(2) an elongation at break is in a range from 60 to 120%,
(3) a dry heat shrinkage stress value is in a range from 0.01 to 0.15 cN/dtex, and
(4) a yarn fineness variation value U % is 1.5% or less and a variation coefficient of a yarn fineness variation period is 0.4 or less.
13. Polyester type drawn conjugate fiber of either a side-by-side type or an eccentric sheath/core type in which two kinds of polyester components are adhered to each other to form a single filament, wherein at least one of the components consisting of the single filament is polytrimethylene terephthalate containing repeating units of trimethylene terephthalate of 90 mol % or more, and wherein the drawn conjugate fiber is wound to form a package and satisfies the following items (5) to (8):
(5) a stretching elongation CE2 measured after the conjugate fiber has been treated with boiling water under a load of 2xc3x9710xe2x88x923 cN/dtex is in a range from 5 to 100%,
(6) an elongation at break is in a range from 25 to 80%,
(7) a dry heat shrinkage stress value is in a range from 0.02 to 0.24 cN/dtex, and
(8) a yarn fineness variation value U % is 1.5% or less and a variation coefficient of a yarn fineness variation period is 0.4 or less.
14. Polyester type conjugate fiber as defined by the above 12 or 13, wherein a fiber-fiber dynamic friction coefficient of the conjugate fiber is in a range from 0.20 to 0.35 and the difference between maximum and minimum values of the dynamic frictional coefficient in the yarn length direction is 0.05 or less.
15. Polyester type conjugate fiber as defined by any one of the above 12 to 14, wherein the difference in the yarn length direction between maximum and minimum values of a stress value at 10% elongation in the measurement of stress and strain is 0.30 cN/dtex or less.
16. Polyester type conjugate fiber as defined by any one of the above 12 to 15, wherein a degree of modified cross-section of the conjugate fiber is in a range from 1 to 5.
17. False-twist textured yarn of polyester type conjugate fiber obtained by the false-twist texturing of the polyester type conjugate fiber defined by any one of the above 1 to 16, satisfying the following items (a) and (b):
(a) a tensile strength is in a range from 2 to 4 cN/dtex, and
(b) a stretching elongation CE2 measured after being treated with boiling water under a load of 2xc3x9710xe2x88x923 cN/dtex is in a range from 50 to 250%.
18. A method for producing a package of polyester type conjugate fiber of either a side-by-side type or an eccentric sheath/core type in which two kinds of polyester components are adhered to each other to form a single filament; at least one of the components consisting of the single filament being polytrimethylene terephthalate containing repeating units of trimethylene terephthalate of 90 mol % or more; and the conjugate fiber being spun by a melt-spinning method and wound in the package while being cooled and solidified by a cooling air, wherein a spinning process is carried out by maintaining a spinning tension at 0.3 cN/dtex or less, a package temperature at 30xc2x0 C. or lower and a winding speed in a range from 1500 to 4000 m/min.
19. A method for producing a package of polyester type pre-oriented conjugate fiber of either a side-by-side type or an eccentric sheath/core type in which two kinds of polyester components are adhered to each other to form a single filament; at least one of the components consisting of the single filament being polytrimethylene terephthalate containing repeating units of trimethylene terephthalate of 90 mol % or more; and the conjugate fiber being spun by a melt-spinning method and wound in the package without drawing the conjugate fiber after being cooled and solidified by a cooling air, wherein the winding is carried out under the condition satisfying the following items (a) to (e):
(a) a spinneret is used to ensure the spinning condition after the two kinds of polyester components join together, having a dimensional ratio L/D of 2 or more wherein L is a hole length and D is a hole diameter and an orifice slanted at an angle from 10 to 40 degrees relative to the vertical direction,
(b) the spinning tension is in a range from 0.10 to 0.30 cN/dtex,
(c) the heat treatment temperature is in a range from 70 to 120xc2x0 C. and the heat treatment tension is in a range from 0.02 to 0.10 cN/dtex,
(d) the package temperature is 30xc2x0 C. or lower when the conjugate fiber is wound onto the winder, and
(e) the winding speed is in a range from 1,500 to 4,000 m/min.
20. A method for producing a package of polyester type drawn conjugate fiber of either a side-by-side type or an eccentric sheath/core type in which two kinds of polyester components are adhered to each other to form a single filament; at least one of the components consisting of the single filament being polytrimethylene terephthalate containing repeating units of trimethylene terephthalate of 90 mol % or more; and the conjugate fiber being spun by a melt-spinning method and wound in the package as drawn conjugate fiber obtained by directly drawing the conjugate fiber without being once wound in the package after being cooled and solidified by cooling air, wherein the winding is carried out under the condition satisfying the following items (a) and (f) to (h):
(a) a spinneret is used to ensure the spinning condition after the two kinds of polyester components join together, having a dimensional ratio L/D of 2 or more wherein L is a hole length and D is a hole diameter and an orifice slanted at an angle from 10 to 40 degrees relative to the vertical direction,
(f) the drawing tension is in a range from 0.05 to 0.40 cN/dtex,
(g) a speed VR of a heated second godet roll is in a range from 2000 to 4000 m/min,
(h) a ratio VW/VR of a winding speed VW (m/min) to the speed VR (m/min) of the heated second godet roll satisfies the following formula (2):
0.85xe2x89xa6VW/VRxe2x89xa61xe2x80x83xe2x80x83(2)
and
(i) the package temperature, when the conjugate fiber is wound onto the winder, is 30xc2x0 C. or lower.
21. A method for producing a package of polyester type conjugate fiber as defined by the above 20, wherein a heat treatment under tension is carried out between a heated second godet roll and a heated third godet roll.
22. A method for producing a package of polyester type conjugate fiber as defined by any one of the above 18 to 21, wherein a traverse angle of the package is changed from the beginning to the completion of the package formation in a range from 3 to 10 degrees in correspondence to the winding diameter of the package.
23. A method for false-twist texturing polyester type pre-oriented conjugate fiber of either a side-by-side type or an eccentric sheath/core type in which two kinds of polyester components are adhered to each other to form a single filament; at least one of the components consisting of the single filament being polytrimethylene terephthalate containing repeating units of trimethylene terephthalate of 90 mol % or more; and the conjugate fiber being spun by a melt-spinning method and wound in the package as pre-oriented conjugate fiber obtained without being drawn after being cooled and solidified by a cooling air, wherein the spinning tension is controlled to 0.30 cN/dtex or less and the package temperature during the winding is maintained at 30xc2x0 C. or lower, and the draw false-twist texturing or the false-twist texturing is carried by maintaining the temperature of the pre-oriented conjugate fiber at 30xc2x0 C. not only during the winding process but also during the storage period as well as the false-twist texturing process thereof.
In this regard, the conjugate fiber referred to in the present invention includes a pre-oriented conjugate fiber which is wound without being drawn after the melt-spinning process and a drawn conjugate fiber which is wound after being continuously spun and drawn (by a so-called direct spin-draw method).
The present invention will be described in more detail below.
The polyester type conjugate fiber package according to the present invention is formed of a group of single filaments in which two kinds of polyester components are adhered to each other in the single filament in a side-by-side manner or an eccentric sheath/core manner wherein at least one component constituting the single filament consists solely of PTT.
The two kinds of polyester components may be adhered to each other in a side-by-side manner along the yarn length direction or may be of an eccentric sheath/core type in which one of the polyester components is partially or totally embedded in the other polyester component so that both the components are arranged in an eccentric manner in the fiber cross-section. The side-by-side type is preferable.
If PTT is used as one component, the crimp development in conjugate fiber or false-twist textured yarn becomes favorable. While there is no limitation in the other component, it is preferably selected from polyethylene terephthalate (PET), polytrimethylene terephthalate (PTT) and polybutylene terephthalate (PBT) in view of the adhesivity with PTT. It is most preferable that both of the two kinds of polyester components are PTT.
The difference in intrinsic viscosity between the two kinds of polyester components is preferably in a range from 0.05 to 0.8 dl/g. When the difference of the intrinsic viscosity is within this range, the crimp development becomes sufficient and yarn bending directly beneath the spinneret is less to minimize the yarn breakage.
When the two kinds of polyester components are PTT, respectively, the difference in intrinsic viscosity is preferably in a range from 0.1 to 0.4 dl/g, more preferably from 0.1 to 0.25 dl/g. An average intrinsic viscosity of the conjugate fiber consisting of PTT is preferably in a range from 0.7 to 1.2 dl/g, more preferably from 0.8 to 1.1 dl/g. If the average intrinsic viscosity is in the above-mentioned range, the strength of the conjugate fiber becomes approximately 2 cN/dtex or more to be applicable to a sportswear field requiring the strength.
In the present invention, a ratio of the two kinds of polyester components in the cross-section of the single filament is preferably in a range from 40/60 to 70/30, more preferably from 45/55 to 65/35 wherein the denominator is a component having a lower intrinsic viscosity and the numerator is a component having a higher intrinsic viscosity. If the ratio is within the above range, the crimp performance is facilitated and a strength of the conjugate fiber is as high as 2.5 cN/dtex or more, which is suitable for sportswear use.
The PTT polymer constituting at least one of the components of the polyester type conjugate fiber according to the present invention contains trimethylene terephthalate repeating units of 90 mol % or more and other ester repeating units of 10 mol % or less.
That is, at least one of the components of the polyester type conjugate fiber according to the present invention is a PTT homopolymer or a PTT copolymer containing 10 mol % or less of other ester repeating units as a copolymeric component.
Examples of the copolymeric component are as follows:
As an acidic component, there are aromatic dicarboxylic acid represented by isophthalic acid or 5-sodiumsulfoisophthalic acid and aliphatic dicarboxylic acid represented by adipic acid or itaconic acid. As a glycolic component, there are ethylene glycol, butylene glycol and polyethylene glycol. Also, hydroxy-carboxylic acid such as hydroxybenzoic acid is an example thereof. A plurality of them may be copolymerized.
A trifunctional cross-linking component, such as trimellitic acid, penthaerythritol or pyromellitic acid, is preferably avoided, in some cases, as a copolymerized component because it disturbs the spinning stability or makes the elongation at break of the false-twist textured yarn lower, resulting in the increase in yarn breakage during the false-twist texturing process.
Known methods may be used for the production of the PTT polymer in the present invention. For example, there are a single-stage method wherein the polymerization degree corresponding to a predetermined intrinsic viscosity is obtained only by the melt-polymerization, and a two-stage method wherein the melt-polymerization is used until a certain intrinsic viscosity is achieved and then the solid-state polymerization is used to increase the polymerization degree to a value corresponding to a predetermined intrinsic viscosity.
The latter two-stage method combined with the solid-state polymerization is preferable because it can reduce the content of cyclic dimer in the polymer. When the predetermined intrinsic viscosity is achieved by the single-stage method, the cyclic dimer in the polymer is preferably reduced prior to being supplied to the spinning process by the extraction treatment or others.
The content of trimetylene terephthalate cyclic dimer in the PTT polymer used for the present invention is preferably 2.5 wt % or less, more preferably 1.1 wt % or less, furthermore preferably 1.0 wt % of less.
Also, additives may be mixed or copolymerized with the PTT polymer within a range not disturbing the effect of the present invention, such as titanium oxide as delusterant, heat stabilizer, anti-oxidant, antistatic agent, ultraviolet absorber, anti-fungus agent or various pigments.
The polyester type conjugate fiber package according to the present invention has a winding weight of 2 kg or more. If the winding weight is less than 2 kg, it is necessary to frequently exchange the packages during the false-twist texturing process or the knitting/weaving process, which is economically disadvantageous because work increases and the operating cost rises. The winding weight is preferably approximately 3 kg or more, more preferably approximately 4 kg or more. The upper limit of the winding weight will be approximately 20 kg in view of the manual handling by the operator although it is not particularly restricted,
The polyester type conjugate fiber package according to the present invention has the difference in winding diameter in a range from 0 to 10 mm between the selvage portion and the central portion of the package. The difference in winding diameter between the selvage portion and the central portion of the package is an index representing a degree of a so-called high-selvage shape. If the winding diameter is smaller than approximately 100 mm, the difference in winding diameter is insignificant. However, if the winding diameter exceeds approximately 200 mm, the difference in winding diameter increases.
When the difference in winding diameter exceeds 10 mm, the yarn fineness variation period becomes significant in a measurement of the yarn fineness variation explained later. If the yarn fineness variation period becomes significant, a periodic dyeing unevenness occurs in the resultant fabric. To prevent the periodic dyeing unevenness from occurring in the fabric, the difference in winding diameter is more preferably 5 mm or less, furthermore preferably 3 mm or less.
The polyester type conjugate fiber package according to the present invention has a winding diameter of 100 mm or more, preferably in a range from 150 to 400 mm. If the winding diameter is 100 mm or more, the winding weight becomes 2 kg or more to provide a package suitable for the industrial use. If the winding diameter is less than 100 mm, the winding weight becomes insufficient to raise the cost of the polyester type conjugate fiber when the price of a paper tube or a bobbin for the package is added thereto. Also, there is an industrial disadvantage in that a wrapping material, a packing cost and a transportation cost for the package become comparatively high.
A winding width of the polyester type conjugate fiber package is in a range from 60 to 250 mm, preferably from 80 to 200 mm. If the winding width is less than 60 mm, the winding diameter must be excessively large to obtain the winding weight of 2 kg or more, resulting in the difficulty of industrial handling thereof. When the winding width is small, a ratio of the selvage portion to the winding width becomes high to cause the high-selvage shaped package. Contrarily, if the winding width exceeds 250 mm, the fluctuation of unwinding tension becomes large during the unwinding of the conjugate fiber from the package even though the high-selvage shape is corrected to be as small as possible, resulting in the periodic dyeing unevenness in the resultant fabric and the yarn breakage during the unwinding of the fiber at a high speed.
The dry heat shrinkage stress of the polyester type conjugate fiber is a shrinking force of the fiber due to heat and measured by a method described later. The polyester type conjugate fiber layered in the selvage portion of the package is liable to have the dry heat shrinkage stress value higher than that of the fiber layered in the central portion of the package.
In the present invention, it is important that the difference in the dry heat shrinkage stress value between fibers layered in the selvage portion and in the central portion is 0.05 cN/dtex or less. If the difference in the dry heat shrinkage stress value exceeds 0.05 cN/dtex, the resultant fabric has the abnormality in the fiber layered in the selvage portion, such as a periodic tight yarn or dyeing unevenness to deteriorate the appearance quality of the resultant fabric. This difference in the dry heat shrinkage stress value is preferable as small as possible, and is preferably 0.01 cN/dtex or less, more preferably 0.005 cN/dtex or less. If there is no difference, it is in the most favorable state.
The preferable aspect of the polyester type conjugate fiber according to the present invention will be described below.
(Variation of Yarn Fineness)
Preferably, in the present invention, the yarn fineness variation value U % of the conjugate fiber unwound from the package is 1.5% or less and the variation coefficient of the yarn fineness variation period is 0.4 or less.
If the yarn fineness variation value U % is 1.5% or less, a fabric excellent in uniformity of dyeing is obtained. The yarn fineness variation value U % is preferably 1.2% or less, more preferably 1.0% or less.
If the variation coefficient is 0.4 or less, a fabric excellent in appearance quality is obtainable. The variation coefficient is preferably as small as possible. Particularly, 0.2% or less is favorable.
When the variation coefficient of the yarn fineness variation period exceeds 0.4 even if the yarn fineness variation value U % is 1.5% or less, the dyeing abnormality occurs in the resultant fabric caused by the selvage portion of the polyester type conjugate fiber package, whereby the fabric having a favorable appearance quality may not be obtainable. For example, a woven fabric having a dense structure of warp and weft yarns is liable to have the above-mentioned dyeing abnormality. Particularly, such an abnormality frequently occurs when the pre-oriented fiber is used as it is for the knitting/weaving process, without being subjected to the draw false-twist texturing process.
As described later, the variation coefficient is determined by the periodic analysis of the yarn fineness variation accompanied with the measurement of the yarn fineness variation.
FIG. 5 is a chart of the periodic analysis of the yarn fineness variation in correspondence to FIG. 3, and FIG. 6 is a chart of the periodic analysis of the yarn fineness variation in correspondence to FIG. 4. In these analysis charts, the horizontal axis represents a periodic length, and the vertical axis represents a frequency (variation coefficient).
In the periodic analysis of the yarn fineness variation, the periodic length corresponds to a yarn length measured from one selvage to the other of the polyester type conjugate fiber package. While the yarn length may vary in accordance with a traverse width when the package is formed, it is generally approximately in a range from 0.5 to 10 m. Signals caused by the yarn fineness variation in the selvage portion appear as specific peaks of the variation coefficient at a constant periodic length as shown in FIG. 6.
(Fluctuation of Unwinding Tension)
The polyester type conjugate fiber package according to the present invention preferably satisfies the following formula which defines the relationship between the difference xcex94F (cN/dtex) in the unwinding tension and the unwinding speed u (m/min) when the conjugate fiber wound in the package is unwound.
xcex94F=8.0xc3x9710xe2x88x926uxe2x80x83xe2x80x83(1)
Formula (1) shows the influence of the unwinding speed on the unwinding tension when the conjugate fiber wound in the package is unwound.
If the difference in the unwinding tension is within the range defined by the formula (1), there is none of the yarn breakage occurring in the knitting/weaving process and the false-twist texturing process due to the fluctuation of unwinding tension or the fabric fault such as tight yarn or dyeing abnormality.
For the purpose of assisting the understanding of the formula (1), an area in which the difference in unwinding tension is favorable is shown by oblique lines in FIG. 9. For instance, if the speed of the fiber unwound from the polyester type conjugate fiber package is 1000 m/min, the difference in unwinding tension xcex94F (cN/dtex) is preferably 0.008 cN/dtex or less.
(Stretching Elongation Prior to Being Treated with Boiling Water)
The stretching elongation Vc prior to being treated with boiling water of the conjugate yarn layered in the selvage portion of the package is preferably 20% or less, more preferably 10% or less.
The conjugate fiber layered in the selvage portion of the package is liable to have a high stretching elongation Vc prior to being treated with boiling water in comparison with the conjugate fiber layered in the central portion. However, if the stretching elongation Vc prior to being treated with boiling water is 20% or less, the unwinding resistance is small when the conjugate fiber is unwound from the package and therefore there is no tension fluctuation or yarn breakage even at a high unwinding speed.
(Winding Hardness)
The winding hardness of the selvage portion of the package is preferably in a range from 50 to 90. Also, the difference in winding hardness between the opposite selvage portions is preferably 10 or less.
When the winding hardness of the selvage portion is within the above-mentioned range, the package is not collapsed during the transportation or handling, and since the unwinding resistance is small when the conjugate fiber is unwound from the selvage portion, there is no tension fluctuation or yarn breakage even at a high unwinding speed. A favorable range of the winding hardness of the selvage portion is from 60 to 85.
When the difference in winding hardness between the opposite selvage portions; that is, between one selvage portion and the other selvage portion; is 10 or less, there is no tight yarn or dyeing abnormality in the resultant fabric because the difference in unwinding tension becomes small between both the selvage portions.
(Winding Density)
The winding density of the package is preferably in a range from 0.80 to 0.92 g/cm3, more preferably from 0.82 to 0.90 g/cm3. When the winding density is within the above-mentioned range, there is no collapse of the package during the transportation or handling thereof, and, as the unwinding resistance becomes small, there is no tension fluctuation or yarn breakage even at a high unwinding speed.
(Bulge)
The bulge percentage of the polyester type conjugate fiber package according to the present invention is preferably 12% or less, more preferably 10% or less, and furthermore preferably 8% or less. of course, it is most preferably 0%.
When the bulge percentage is 12% or less, the winding tightness of the package due to the shrinkage of the conjugate fiber is less, whereby it is possible to easily remove the package from a spindle of the winder. Also, as the package end is not brought into contact with the wrapping material when the package is bundled, the conjugate fiber is smoothly unwound from the package during the unwinding process.
Conditions peculiar to the polyester type pre-oriented conjugate fiber package according to the present invention will be described below.
The polyester type pre-oriented conjugate fiber is wound in a package and simultaneously satisfies the following items (1) to (4):
(1) the stretching elongation Vc prior to being treated with boiling water is less than 20%,
(2) the elongation at break is in a range from 60 to 120%,
(3) the dry heat shrinkage stress value is in a range from 0.01 to 0.15 cN/dtex), and
(4) the yarn fineness variation value U % is 1.5% or less and the variation coefficient of the yarn fineness variation period is 0.4 or less.
In the present invention, the stretching elongation Vc prior to being treated with boiling water of the polyester type pre-oriented conjugate fiber is less than 20%, preferably 15% or less, and more preferably 10% or less. If the stretching elongation Vc prior to being treated with boiling water is less than 20%, a contact resistance of the fiber with guides or others becomes small during the high-speed false-twist texturing process or the high-speed draw false-twist texturing process and thereby no yarn breakage or fluff generates.
In the present invention, the elongation at break of the polyester type pre-oriented conjugate fiber is in a range from 60 to 120%, preferably from 70 to 100%. The pre-oriented conjugate fiber having the elongation at break within the above-mentioned range is obtainable at a winding speed of approximately 4000 m/min or less to form a package having a smaller selvage height which does not collapse even if it is stored for a long time.
In the present invention, the dry heat shrinkage stress value of the polyester type pre-oriented conjugate fiber is in a range from 0.01 to 0.15 cN/dtex, preferably from 0.03 to 0.10 cN/dtex. If the dry heat shrinkage stress value is within the above-mentioned range, a package having a smaller selvage height is formed which is free from yarn breakage during the winding thereof. While the dry heat shrinkage stress value is preferably as small as possible, it is difficult to produce the fiber having the dry heat shrinkage stress value of less than 0.01.
In the present invention, the yarn fineness variation value U % of the polyester type pre-oriented conjugate fiber is 1.5% or less and the variation coefficient of the yarn fineness variation period is 0.4 or less.
If the yarn fineness variation value U % is 1.5% or less, the resultant fabric is excellent in dyeing uniformity. The yarn fineness variation value U % is preferably 1.2% or less, more preferably 1.0% or less.
If the variation coefficient is 0.4 or less, the resultant fabric is excellent in appearance quality. The variation coefficient is preferably as small as possible. 0.3 or less is particularly favorable.
When the variation coefficient of the yarn fineness variation period exceeds 0.4, a dyeing abnormality may occur in the resultant fabric caused by the selvage portion of the polyester type conjugate fiber package, even if the variation coefficient U % is 1.5% or less, to deteriorate the appearance quality of the fabric. For example, in the woven fabric in which warp yarns and weft yarns are densely interwoven, this dyeing abnormality is liable to occur. Particularly, this phenomenon is significant when the pre-oriented conjugate fiber is supplied to the knitting/weaving process as it is without being subjected to the draw false-twist texturing process.
The crystallization calorific value measured by the differential scanning calorimetry (DSC) of the polyester type pre-oriented conjugate fiber is preferably 10 J/g or less, more preferably 5 J/g or less, furthermore preferably 2 J/g or less. If the crystallization calorific value is 10 J/g or less, the progression of self-crystallization of the pre-oriented conjugate fiber at a high temperature is restricted. The crystallization calorific value is preferably as small as possible.
The crystallization calorific value by the differential scanning calorimetry (DSC) is a value obtained by the measurement described later. The crystallization calorific value is a calorie generated when the pre-oriented conjugate fiber is crystallized, which is a measure of the degree of crystallization. The smaller the crystallization calorific value, the more the crystallization of the pre-oriented conjugate fiber.
The crystallization calorific value of the polyester type pre-oriented conjugate fiber in which the crystallization is hardly progressed exceeds approximately 10 J/g. On the other hand, when the crystallization has sufficiently progressed, the crystallization calorific value becomes 0 J/g according to this method, and the measurement is impossible.
One of the advantages of the pre-oriented conjugate fiber in which the crystallization has been progressed is that when the pre-oriented conjugate fiber is fed to the draw false-twist texturing process and maintained in a hot environment at approximately 40xc2x0 C. or higher for a long time, the progression of the self-crystallization of the pre-oriented conjugate fiber is restricted. According to this effect, the high-selvage shape and the deformation of the package are reduced whereby the occurrence of the dyeing abnormality of the false-twist textured yarn is minimized.
Another advantage is that the pre-oriented conjugate fiber can be fed to the knitting/weaving process without being subjected to the draw false-twist texturing process to result in a fabric excellent in appearance quality.
Next, conditions peculiar to the polyester type drawn conjugate fiber package according to the present invention will be described below.
The polyester type drawn conjugate fiber is wound in a package and simultaneously satisfies the following items (5) to (8):
(5) the stretching elongation CE2 measured under a load of 2xc3x9710xe2x88x923 cN/dtex after being treated with boiling water is in a range from 5 to 100%.
(6) the elongation at break is in a range from 25 to 80%,
(7) the dry heat shrinkage stress value is in a range from 0.02 to 0.24 cN/dtex, and
(8) the yarn fineness variation value U % is 1.5% or less and the variation coefficient of the yarn fineness variation period is 0.4 or less.
In the present invention, the stretching elongation CE2 measured under a load of 2xc3x9710xe2x88x923 cN/dtex after being treated with boiling water is in a range from 5 to 100%, preferably from 10 to 100%, more preferably from 20 to 100%. If the stretching elongation CE2 is within the above-mentioned range, the resultant fabric is excellent in stretchability. In this regard, it is difficult to achieve 100% or more of this value according to the present technology.
The larger the stretching elongation CE2, the higher the stretchability even in a fabric of a structure having a high restriction force such as a woven fabric.
In the present invention, the elongation at break of the polyester type drawn conjugate fiber is in a range from 25 to 80%, preferably from 30 to 60%. If the elongation at break is 25% or more, it is possible to produce the fiber in a stable manner without yarn breakage during the drawing, and a package thereof has a low selvage height whereby no dyeing abnormality occurs in the resultant fabric. If the elongation at break is 80% or less, the tensile strength of the conjugate fiber is approximately 2 cN/dtex or more and is usable for a sportswear application requiring the high strength. Also, there is no dyeing abnormality of thick-and-thin type.
In the present invention, the dry heat shrinkage stress value of the polyester type drawn conjugate fiber is in a range from 0.02 to 0.24 cN/dtex, preferably from 0.05 to 0.15 cN/dtex. If the dry heat shrinkage stress value is within the above-mentioned range, it is possible to form a package having a low selvage height.
The dry heat shrinkage stress value is preferably as small as possible. However, the production of the fiber having this value of less than 0.02 is difficult because the yarn breakage often occurs during the winding.
In the present invention, the yarn fineness variation value U % of the drawn conjugate fiber is 1.5 or less and the variation coefficient of the yarn fineness variation period there of is preferably 0.4 or less.
If the yarn fineness variation value U % is 1.5% or less, a fabric excellent in dyeing uniformity is obtainable. The yarn fineness variation value U % is preferably 1.2% or less, more preferably from 1.0% or less.
If the variation coefficient is 0.4 or less, a fabric excellent in appearance quality is obtainable. The variation coefficient is preferably as small as possible, and 0.3 or less is particularly favorable.
When the variation coefficient of the yarn fineness variation period exceeds 0.4, there may be a case in that the dyeing abnormality occurs in the resultant fabric due to the selvage portion of the drawn conjugate fiber package to degrade the fabric even if the yarn fineness variation value U % is 1.5% or less. For example, this tendency is significant in a woven fabric in which warp yarn and weft yarns are densely interwoven, particularly, when the drawn conjugate fiber is fed to the knitting/weaving process as it is without being subjected to the false-twist texturing process.
Favorable conditions common to the polyester type pre-oriented conjugate fiber and the polyester type drawn conjugate fiber will be described below:
Preferably, the fiber-fiber dynamic friction coefficient is in a range from 0.20 to 0.35 and the difference therein between maximum and minimum values in the yarn length direction is 0.05 or less.
If the fiber-fiber dynamic friction coefficient is within the above-mentioned range, it is possible to form a package of 2 kg or more since the fiber does not slip off from the package. Also, since the unwinding tension becomes small when the conjugate fiber is unwound from the package, there is no yarn breakage or dyeing abnormality.
If the difference in the coefficient of friction between maximum and minimum values in the yarn length direction is 0.5 or less, it is possible to further reduce the fluctuation of the unwinding tension.
The difference in stress value at 10% elongation in the stress-strain measurement between maximum and minimum values is preferably 0.30 cN/dtex or less in the yarn length direction. The present inventors have found that the stress value at 10% elongation in the stress-strain measurement has a good correspondence with the dyeing uniformity in the yarn length direction and if the difference between the maximum and minimum values is 0.30 cN/dtex or less in the yarn length direction, a fabric excellent in dyeing uniformity is obtainable. The difference in stress value at 10% elongation between maximum and minimum values is preferably as small as possible, and if it is 0.2 cN/dtex or less, a fabric further excellent in dyeing uniformity is obtainable.
While there is no limitation in the yarn fineness or a single filament fineness of the polyester type conjugate fiber, the yarn fineness is preferably in a range from 20 to 300 dtex and the single filament fineness is preferably in a range from 0.5 to 20 dtex.
There is no limitation in the single filament cross section, which may include modified cross section other than a circle, such as a triangle, an oval, a flat shape, a W-shape or an X-shape. Particularly, it is possible to exhibit excellent dyeing uniformity as well as good stretchability if the degree of modified cross section is in a range from 1 to 5.
In the present invention, the polyester type conjugate fiber may be used as a long filament yarn or staple fibers cut into a length in a range from 20 to 200 mm. In either cases, excellent dyeing uniformity as well as good stretchability are obtainable.
The polyester type conjugate fiber according to the present invention may be mixed or copolymerized with titanium oxide as delusterant, thermal stabilizer, antioxidnat, antistatic agent, ultraviolet absorber, antifungus agent or various pigment unless it disturbs the effect of the present invention.
Also, a finishing agent in a range from 0.2 to 2 wt % is preferably applied to the polyester type conjugate fiber for the purpose of imparting the fiber with smoothness, filament cohesion and antistatic property. Further, for the purpose of improving the unwinding property and the filament cohesion during the unwinding or false-twist texturing process, the single filaments may be interlaced with each other at 2 to 50 points/m.
A method for producing the polyester type conjugate fiber package according to the present invention will be described below.
The polyester type conjugate fiber package according to the present invention can be produced by a conjugate fiber spinning apparatus including a spinneret and a two-shaft extruder described below.
FIG. 10 illustrates a schematic view of one example of a spinneret used for the production of the polyester type conjugate fiber package according to the present invention.
In FIG. 10, (a) denotes a distributor and (b) denotes a spinning nozzle. The two kinds of polyesters having different intrinsic viscosity values are introduced from P and Q, respectively, and fed to the spinning nozzle (b) from the distributor (a). After the both are joined together in the spinning nozzle (b), the joined stream is extruded from the spinning orifice slanted at xcex8 degrees relative to the vertical direction. A diameter of the orifice is represented by D and a length thereof is represented by L.
In the present invention, a ratio of the length L to the diameter D (L/D) is preferably 2 or more. If L/D is 2 or more, both the components having different intrinsic viscosity values are stably adhered to each other after being joined together whereby no vibration occurs in the extruded stream. Thus, it is possible to maintain the yarn fineness variation value U % of the resultant fiber within the range defined by the present invention. L/D is preferably as large as possible. However, in view of the ease of manufacture of the spinneret, L/D is more preferably in a range from 2 to 8, furthermore preferably from 2.5 to 5.
In the present invention, the spinning orifice has the inclination in a range from 10 to 40 degrees relative to the vertical direction. The inclination angle of the spinning orifice relative to the vertical line is represented by xcex8 (degrees) in FIG. 10.
This inclination of the spinning orifice relative to the vertical direction is an important condition for preventing the yarn bending from occurring due to the difference in intrinsic viscosity between the two kinds of polyester components. If there is no inclination in the spinning orifice, the filament yarn as extruded from the orifice is liable to bend toward the higher intrinsic viscosity side as the difference in intrinsic viscosity is larger. This is called a bending phenomenon which disturbs the stable spinning. Also, the yarn fineness variation value U % of the resultant conjugate fiber becomes larger to deteriorate the dyeing uniformity.
In FIG. 10, preferably, the polyester having a higher intrinsic viscosity is supplied to the side P and that having a lower intrinsic viscosity is supplied to the side Q.
FIG. 11 is a schematic illustration of one example of a spinning apparatus used for carrying out the method according to the present invention. Based on this drawing, a preferable production method will be described.
In FIG. 11, pellets of one polyester component are dried by a dryer 1 to have a moisture content of 20 ppm or less and supplied to an extruder 2 maintained at a temperature in a range from 250 to 280xc2x0 C. in which the pellets are melted. Pellets of the other polyester component are also supplied to an extruder 4 via a dryer 3 and melted in the same manner as before.
The melted polyester components are supplied via bends 5 and 6, respectively, to a spin head 7 maintained at a temperature in a range from 250 to 285xc2x0 C., and weighed separately by gear pumps. Then, the two kinds of components are joined together in a spinneret 9 which has a plurality of orifices and is mounted to a spinning pack 8. After they are adhered with each other to form a side-by-side type or an eccentric sheath/core type conjugate fiber, the components are extruded in a spinning chamber as a filament yarn of the conjugate fiber 10.
The optimum temperature of the extruder and the spin head is selected from the above-mentioned range in accordance with kinds or intrinsic viscosity values of the polyester.
The filament yarn 10 extruded into the spinning chamber is cooled, by cooling air 12, to room temperature and solidified. After being imparted with a finishing agent by a finishing agent applicator 13, the filament yarn is taken up by a first godet roll 14 rotating at a predetermined speed.
The finishing agent is preferably of an aqueous emulsion type, a concentration of which is preferably 10 wt % or more, more preferably in a range from 15 to 30 wt %. The finishing agent preferably contains fatty acid ester and/or mineral oil in a range from 10 to 80 wt % or polyether having a molecular weight of 1000 to 20000 in a range from 50 to 98 wt %, which is preferably imparted to the fiber in a range from 0.3 to 1.5 wt %. By the application of such a finishing agent, it is possible to control the fiber-fiber dynamic friction coefficient within a range from 0.2 to 0.35 so that the unwinding property of the conjugate fiber from the package is improved and yarn breakage is prevented from occurring during the false-twist texturing process or the knitting/weaving process.
If necessary, an interlacer may be provided between the finishing agent applicator 13 and the first godet roll 14, between the first godet roll 14 and a second godet roll 15 or between the second godet roll 15 and a winder to impart the yarn with intermingling. The interlacer may be of a known type wherein a fluid pressure is preferably adjusted to a value in a range from 0.01 to 0.6 MPa to impart the yarn with intermingling in a range from 2 to 50 points/m.
According to the present invention, the spinning tension is 0.30 cN/dtex or less, preferably 0.20 cN/dtex or less, more preferably 0.15 cN/dtex or less. The spinning tension is preferably as small as possible. However, if this value is 0.3 cN/dtex or less, it is possible to continuously produce the fiber in a stable state because there is no yarn breakage caused by the frictional abrasion of the fiber with the finishing agent applicator.
The spinning tension is a value dividing a yarn tension (cN) measured at a position apart downward from the finishing agent applicator 13 in FIG. 11 by approximately 10 cm by the yarn fineness (dtex) of the conjugate fiber on the take-up godet roll.
The spinning tension is suitably adjustable in accordance with the collecting methods of the filament yarn. For example, the spinning tension may be adjustable in accordance with spinning speeds, distances from the spinneret to a position at which the yarn is collected, and kinds of collecting guides. The application of the finishing agent is preferably carried out simultaneously with the collection of the filament yarn.
In the production method according to the present invention, it is important that the winding package is maintained at a temperature of 30xc2x0 C. or lower. By maintaining the temperature of the winding package at 30xc2x0 C. or lower, it is possible to eliminate a high-selvage shape of the package or the drawbacks of the fiber in the selvage portion of the package due to the shrinkage of the conjugate fiber. If the package temperature exceeds 30xc2x0 C., the variation coefficient of the yarn fineness variation period becomes larger than 0.4 even though the yarn fineness variation value U % is suppressed as low as possible, whereby the object of the present invention is not achievable. This fact has been found for the first time by the present inventors and is one of important characteristics of the present invention. As the package temperature during winding exceeds approximately 40xc2x0 C. in the prior art high speed winding, the drawbacks of the fiber in the selvage portion have not been eliminated.
The package temperature is preferably maintained at 30xc2x0 C. or lower from the commencement to the completion of the winding operation. As means for maintaining the package temperature at 30xc2x0 C. or lower, heat conduction and heat radiation from a motor which is a drive source of the winder and a heat-generation source for the bobbin shaft are preferably intercepted. In addition, the winding package and the surrounding area thereof are preferably cooled by cooling air for achieving the above object.
The package temperature during winding is preferably as low as possible. Approximately 25xc2x0 C. or lower is more preferable. Since a large amount of energy is necessary for maintaining an excessively low temperature, the package temperature is more preferably in a range from approximately 20 to 25xc2x0 C.
According to the production method according to the present invention, the winding speed is in a range from 1500 to 4000 m/min, preferably from 1800 to 3500 m/min, more preferably from 2000 to 3300 m/min. If the winding speed is within the above range, the degree of orientation of the conjugate fiber being spun is sufficiently high and the yarn fineness variation value U % and the yarn fineness variation coefficient are within the range defined by the present invention. Also, since the spinning tension and the drawing tension are not retained in the wound fiber, the difference in the dry heat shrinkage stress value between the selvage portion and the central portion of the package is 0.05 cN/dtex or less to achieve the object of the present invention. When the heat treatment is carried out during the winding process, the tension is maintained at 0.02 cN/dtex or more to minimize the yarn fineness variation, whereby no yarn breakage or fluff generates, even though the heat treatment temperature exceeds 70xc2x0 C.
Next, conditions peculiar to the method for producing the polyester type pre-oriented conjugate fiber package according to the present invention will be described below.
In FIG. 11, the conjugate fiber taken up by the first godet roll 14 is wound as a pre-oriented conjugate fiber package 16 via a second godet roll 15 without being substantially drawn.
At least one of the first godet roll 14 and the second godet roll 15 is preferably heated as a hot godet roll so that the pre-oriented conjugate fiber is heat-treated prior to being wound in the package. The heat treatment is not limited to only that using the hot godet roll but may be carried out by any method provided the fiber can be heat-treated before it is wound in the package.
The heat-treatment condition for the pre-oriented conjugate fiber is preferably in that the heat-treatment temperature is in a range from 70 to 120xc2x0 C. and the heat-treatment tension is in a range from 0.02 to 0.1 cN/dtex. The heat treatment is preferably carried out by wrapping the pre-oriented conjugate fiber 2 to 10 times around the hot godet roll. In this case, the temperature of the hot godet roll is preferably maintained at a level generally equal to the heat-treatment temperature of the pre-oriented conjugate fiber.
If the heat-treatment temperature is 70xc2x0 C. or higher, the crystallization calorific value of the resultant pre-oriented conjugate fiber is 10 J/g or less so that the object of the present invention is more effectively achievable. When the heat-treatment temperature exceeds 120xc2x0 C., the yarn vibration becomes significant on the godet roll because the pre-oriented conjugate fiber having a low crystallization degree is abruptly brought into contact with the high temperature to cause the generation of fluff or yarn breakage, whereby it is difficult to maintain stable production. Also, the yarn fineness variation value U % of the resultant pre-oriented fiber exceeds 1.5%. Thus, the heat-treatment temperature is preferably in a range from 80 to 110xc2x0 C., more preferably from 90 to 110xc2x0 C.
The heat-treatment tension of the pre-oriented conjugate fiber is measured on the hot godet roll or at a position directly after it departs from the hot godet roll. The adjustment of this tension is carried out by regulating the temperature and the speed of the hot godet roll. If the heat-treatment tension is within the above-mentioned range, the yarn vibration on the godet roll is minimized and the running of the pre-oriented conjugate fiber becomes stable. Also, there is no tight winding of the package. The heat-treatment tension is preferably in a range from 0.03 to 0.07 cN/dtex.
While there is no limitation in the heat-treatment time, a range from approximately 0.01 to 0.1 second is generally employed.
Next, conditions peculiar to the method for producing the polyester type drawn conjugate fiber package according to the present invention will be described below.
In FIG. 11, when the polyester type drawn conjugate fiber package is produced, the conjugate fiber taken up by the first godet roll 14 is continuously drawn by the second godet roll without being once wound in a package, and then wound by the winder to form a predetermined drawn conjugate fiber package 16.
During the drawing, a temperature of the first godet roll 14 is preferably maintained in a range from 50 to 90xc2x0 C., more preferably from 55 to 70xc2x0 C. The second godet roll 15 is heated so that the drawn yarn is heat-treated by the second godet roll 15. The heat-treatment temperature is preferably in a range from 90 to 160xc2x0 C., more preferably from 100 to 140xc2x0 C.
In the present invention, it is necessary that the drawing tension is in a range from 0.05 to 0.40 cN/dtex, preferably from 0.10 to 0.30 cN/dtex. If the drawing tension is within the above range, the polyester type drawn conjugate fiber has a sufficient tensile strength of approximately 1.5 cN/dtex. Also, the elongation at break thereof is 30% or more whereby no fluff or yarn breakage occurs during the drawing. The drawing tension is defined by a speed ratio between the first godet roll 14 and the second godet roll 15.
The drawing tension is determined by selecting the combination of a ratio in the peripheral speed between the first and second godet rolls; i.e., a draw ratio; and the temperature of the first godet roll. When the first godet roll has a speed in a range from 1500 to 3000 m/min and a temperature in a range from 50 to 90xc2x0 C., the drawing tension in a favorable range is obtainable by adjusting the draw ratio to a value in a range from 1.4 to 2.5 times. The draw ratio is preferably in a range from 1.4 to 2.0 times. According to a known direct spin-draw method, the drawing tension reaches as high as approximately 0.5 cN/dtex or more when the draw ratio is in a range from 3 to 5 times. Contrarily, according to the present invention, the drawing is carried out at a further low drawing tension.
In the present invention, the peripheral speed VR of the hot second godet roll 15 is preferably in a range from 2000 to 4000 m/min, more preferably from 2400 to 3300 m/min. If the peripheral speed VR is within the above range, it is possible to cause the first godet roll to rotate at a peripheral speed of 1500 m/min or more, whereby the vibration of the filament yarn becomes small to stabilize the running of the yarn during the spinning and the drawing. Also, as the shrinkage of the polyester type drawn conjugate fiber is minimized during the winding or after being wound in the package, the height of the selvage portion of the package is low to reduce the tension fluctuation when the fiber is unwound from the package at a high speed.
Two or three pairs or more of the godet rolls are used in the present invention. A pair of pretension rolls may be provided in front of the take-up godet roll. An apparatus suitable for producing the polyester type drawn conjugate fiber is that having three pairs of godet rolls as shown in FIG. 12.
A third godet roll 17 may be either heated or non-heated. However, the hot godet roll is preferable for the purpose of obtaining the dry heat shrinkage stress value in a range from 0.02 to 0.24 cN/dtex of the polyester type drawn conjugate fiber and facilitating the stretching elongation CE2 thereof. When the hot third godet roll is used, the temperature thereof is preferably in a range from 50 to 180xc2x0 C., more preferably from 90 to 150xc2x0 C. If the temperature is within this range, the winding is carried out in a stable state without the occurrence of yarn breakage.
In the present invention, if the heat set is carried out between the second godet roll 15 and the third godet roll 17 under the tension in a range from 0.05 to 0.5 cN/dtex, it is possible to make the stretching elongation CE2 as high as 5% or more. The tension between the second godet roll 15 and the third godet roll 17 can be determined by a speed ratio between the both. The speed ratio between the second and third godet rolls is preferably in a range from 1.0 to 1.1.
In the present invention, the winding is preferably carried out so that a ratio VW/VR satisfies the following formula (2):
0.85xe2x89xa6VW/VRxe2x89xa61xe2x80x83xe2x80x83(2)
wherein VW is a winding speed and VR is a speed of the hot second godet roll.
To assist the understanding of the formula (2), a favorable area is shown in FIG. 13 in relation to VR and VW/VR. In FIG. 13, a horizontal axis represents the speed VR of the second godet roll and a vertical axis represents the ratio VW/VR. That is, the speed ratio VW/VR means a relax ratio from the second godet roll to the winder.
In the present invention, the ratio VW/VR is preferably 0.85 or more. If the ratio VW/VR is less than 0.85, the tension lowers between the second godet roll and the winder, which may disturb the stable winding. The ratio VW/VR is preferably in a range from 0.90 to 0.96.
In the present invention, the winding is preferably carried out satisfying the formula (2) at a speed ratio so that the winding tension between the second godet roll 15 and the winder in FIG. 11 or between the third godet roll and the winder in FIG. 12 becomes preferably in a range from 0.02 to 0.12 cN/dtex, more preferably from 0.04 to 0.07 cN/dtex. If the winding tension is within the above range, a high-selvage shaped package or a bulged package does not result.
According to the production method of the present invention, the traverse angle is changed preferably in a range from 3 to 10 degrees, more preferably from 4 to 9 degrees from the commencement to the completion of the package formation in accordance with the respective winding diameters of the package. If the traverse angle is within the above range, no collapse occurs whereby a normal-shaped package is obtainable, free from a high-selvage portion. The traverse angle is determined by adjusting the winding speed and the traverse speed.
In the present invention, the traverse angle in the middle yarn layer of the package is preferably larger than that in the innermost yarn layer. In this regard, the innermost yarn layer of the package is a layer existing within a thickness of approximately 10 mm from the bobbin surface. According to the most favorable aspect for changing the traverse angle in accordance with the winding diameters, the traverse angle is small at the beginning of the winding; i.e., in the innermost yarn layer of the package; and gradually increases as the enlargement of the winding diameter to reach the maximum value in the middle yarn layer, after which the traverse angle reduces again in the outermost yarn layer. By changing the traverse angle in accordance with the winding diameter in such a manner, it is possible to sufficiently minimize both of the bulge and the high-selvage of the package.
The above-mentioned method for winding the yarn while changing the traverse angle in accordance with the winding diameters is also applicable to the method for producing the polyester type pre-oriented conjugate fiber described before, and results in a favorable effect.
A method for producing a false-twist textured yarn of the polyester type conjugated fiber according to the present invention will be described below.
This method is most effective for the false-twist texturing process of the polyester type pre-oriented conjugate fiber.
In the present invention, when the polyester type pre-oriented conjugate fiber in the package is subjected to the draw false-twist texturing process or the polyester type drawn conjugate fiber in the package is subjected to the false-twist texturing process, the temperature of the package is maintained at 30xc2x0 C. or lower, preferably 25xc2x0 C. or lower, throughout all the processes including the winding, the storage and the false-twist texturing. If the temperature is within the above range, no high-selvage occurs in the package during the period from the storage to the false-twist texturing, whereby a false-twist textured yarn excellent in appearance quality is obtainable.
The false-twist texturing process may be of a conventional type such as a pin type, a friction type, a nip-belt type or an air twist type. While a false-twist texturing heater may be either of a single heater type or a double heater type, the former type is favorable for the purpose of obtaining a high stretchability.
The heater temperature is determined so that a yarn temperature becomes 130 to 200xc2x0 C., preferably 150 to 180xc2x0 C., more preferably 160 to 180xc2x0 C. measured at a position directly after an exit of the first heater.
The false-twist texturing heater may be of a touch type or a non-touch type.
The stretching elongation CE2 of the false-twist textured yarn obtained by the single-heater type false-twist texturing process is preferably in a range from 50 to 250% and a stretching modulus is preferably 80% or more.
If necessary, a second heater may be used for the heat setting to obtain a double-heater-type false-twist textured yarn. The temperature of the second heater is preferably in a range from 100 to 210xc2x0 C., more preferably in a range from xe2x88x9230 to +50xc2x0 C. relative to the yarn temperature measured at a position directly after an exit of the first heater.
An overfeed ratio in the second heater (a second overfeed ratio) is preferably in a range from +3% to +30%.
The false-twist textured yarn of the polyester type conjugate fiber in the inventive package is good in appearance and free from dyeing unevenness as well as excellent in stretchability and stretch-back property.
For example, the stretching elongation of apparent crimp which is visible prior to being treated with boiling water is in a range from 50 to 300%. It is important that the fiber has a large apparent crimp visible prior to being treated with boiling water, for obtaining a fabric excellent in elongation recovery; i.e., the stretchability and instantaneous recovery; because such a fiber can remarkably develop crimps, by the boiling water treatment, even if it is used in a fabric having a large restriction force such as a woven fabric.
If the false-twist textured yarn of the polyester type conjugate fiber obtained by the present invention is used for a weft yarn, a gray fabric prior to being treated with boiling water also has the stretchability as well as a resultant woven fabric has. This property has never been seen in a conventional woven fabric in which known false-twist textured yarn or latent crimp conjugate fiber is used.
The false-twist textured yarn of the polyester type conjugate fiber obtained by the present invention has the stretching elongation CE2 measured under a load of 2xc3x9710xe2x88x923 cN/dtex after being treated with boiling water in a range from 50 to 250% and exhibits a high crimp development property, which is one of characteristic of the present invention.
It will be understood that the false-twist textured yarn according to the present invention exhibits an extremely high crimp performance in comparison with a fact that a known false-twist textured yarn obtained by false-twist texturing a conventional fiber consisting solely of PTT has the stretching elongation of approximately 30%.
Further, another characteristic of the polyester type conjugate fiber is that the elongation recovery speed, after being treated with boiling water, is in a range from 20 to 50 m/sec which is a proof of the excellent instantaneous recovery. The stretching recovery speed is measured in such a manner that, after the false-twist textured yarn of the polyester type conjugate fiber is treated with boiling water under no load, the crimp thereof is stretched until a stress reaches a predetermined value, after which the fiber is severed and a speed at which the fiber returns to the original length is measured. The larger the stretching recovery speed, the faster the stretching recovery of the fabric; that is, the more excellent the adaptability to the body movement when the yarn is used for the clothing fabric.
If the stretching recovery speed is 15 m/sec or more in the knitted fabric and 20 m/sec or more in the woven fabric, the fabric excellent in adaptability to the body movement is obtainable. If the stretching recovery speed is less than this value, the adaptability to the body movement becomes insufficient when the yarn is knitted or woven into the fabric. The stretching recovery speed is preferably 20 m/sec or more in the knitted fabric and 25 m/sec or more in the woven fabric. As apparent from a fact that the stretching recovery speed of a known spandex type elastomeric fiber is in a range from approximately 30 to 50 m/sec, it will be understood that the false-twist textured yarn of the polyester type conjugate fiber according to the present invention has the stretching recovery as good as the spandex type elastomeric fiber. In this regard, it is difficult, at the present technical level, to produce a fiber having the stretching recovery speed of 50 m/sec or more.
The stretching recovery speed of a known PET type false-twist textured yarn is approximately 10 m/sec, and that of a false-twist textured yarn of a fiber consisting solely of PTT is approximately 15 m/sec.
The measurement of the stretching recovery speed described above has been invented by the present inventors, and the stretch-back property was quantitatively measured for the first time.
A fabric obtained by using the polyester type conjugate fiber according to the present invention which is not subjected to the false-twist texturing process is also free from periodic dyeing unevenness and good in appearance quality as well as soft hand touch.
The polyester type conjugate fiber according to the present invention may be used for forming all of a fabric, or may be mixed with other fibers and used for forming part of the fabric. The other fibers to be mixed therewith are, for example, polyester fiber, cellulose fiber, nylon 6 fiber, nylon 66 fiber, acetate fiber, acrylic fiber, polyurethane elastomeric fiber, wool or silk including a filament type and a staple fiber type, but should not be limited thereto.
To obtain a mixed fiber composite yarn by mixing or combining the polyester type conjugate fiber according to the present invention with other fibers, various methods may be employed; for example, a method in which the inventive fiber is interlace-mixed with other fibers; a method in which the interlace-mixed fibers are draw false-twist textured; a method in which one of the fibers is false-twist textured and then interlace-mixed with the other; a method in which both fibers are separately false-twist textured and then interlace-mixed together; a method in which one of the fibers is Taslan-processed and then interlace-mixed with the other; and a method in which both fibers are Taslan-mixed. The mixed fiber composite yarn obtained by the above methods is preferably has intermingling portions of 10 point/m or more.